Development of Aquatic Index of Biotic Integrity and Its Driving Factors in the Diannong River, China

Round 1

Reviewer 1 Report

The manuscript is well written but the reviewer has some major concerns.

1. Rather than using "construction" words use "Development" words.

2. Please make a table or graph on water quality parameters and make the correlation analysis of each metric with water quality parameters.

3. Why the phytoplankton index is not influenced by nutrients (TP, TN) or organic matter (BOD, COD)? Please explain it.

4.  How did you calculate the habitat composite and water quality index score? Give a detailed explanation with row data so readers can see your all site's metrics values. 

Author Response

Response to Reviewer 1 Comments

Dear Reviewers:

Thanks for your comments concerning our manuscript entitled “Construction of Aquatic Index of Biotic Integrity and Its Driving Factors in the Diannong River, China” (ID: water-2256894). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and made corrections, which we hope meet with approval. Revised portions are marked in red on the paper. The main corrections in the paper and the responses to the reviewer’s comments are as follows (references are at the end of the document):

Point 1: Rather than using "construction" words use "Development" words.

Response 1: Thanks for your advice, we totally agree that the terms we used were not inappropriate, so we have replaced the corresponding positions (Line 2, 57, 71, 88, 105, 107, 210, 283, 410, 419, 441, 466) .

Point 2: Please make a table or graph on water quality parameters and make the correlation analysis of each metric with water quality parameters.

Response 2: Thanks to the reviewer for pointing it out. We neglected the importance of showing water environmental parameters and their inner relationship for understanding manuscript if reviewers and other viewers read it. We have supplemented corresponding figures and described the change conditions of water environmental parameters (Line 255-265, 274-280).

Point 3: Why the phytoplankton index is not influenced by nutrients (TP, TN) or organic matter (BOD, COD)? Please explain it.

Response 3: Thanks for your question. We initially just defaulted the results of stepwise regression analysis by statistic process rather than explaining this relative perverse phenomenon. In freshwater ecosystems, there are several factors that influence the structural characteristics of aquatic plant communities, including phytoplankton, which can be classified into two categories: physical and chemical factors. The physical factors include light, water temperature and transparency, while the chemical factors include total nitrogen, total phosphorus, pH, COD, etc. However, TP has a higher impact on phytoplankton community structure than nutrients represented by TN and organic matter represented by COD and BOD, and is a limiting factor for phytoplankton growth and reproduction [1]. The relative small variation of TP index in the Diannong River could be attributed to two reasons: on the one hand, the small variation of elevation along the Diannong River and the slow flow of the water body resulted in the small variation of TP along the Diannong River. On the other hand, most of the Diannong River was a landscape river and the surrounding residential land was less, so the less discharge of domestic sewage, which was the main source of TP pollution in the water body, was also one of the main reasons for the relative small change of TP. Therefore, the stepwise regression analysis on P-IBI screened out TP and TN. Meanwhile, the correlation analysis between the water environment factors showed that TP was significantly correlated with COD_Cr and COD_Mn (Line 254), so the stepwise regression analysis also screened out COD_Cr and COD_Mn.

Point 4: How did you calculate the habitat composite and water quality index score? Give a detailed explanation with row data so readers can see your all site's metrics values. 

Response 4: Thanks for your comment and request. In the initial manuscript, we only presented the results of habitat composite index and water scores in the form of figures to avoid stating the results redundantly, but we ignored the importance of readers to understand manuscript methodology in detail. We have submitted corresponding detailed explanation with raw data by supplement table in the additional file (Line 193, 204-205).

We have tried our best to improve the manuscript and made some changes, and we hope that the correction will meet with approval. Meanwhile, we appreciate for reviewer’s warm work earnestly. Once again, thank you very much for your comments and suggestions.

Sincerely yours

Lin Lee

Reference

1. Zhang J.T. Applied Ecology. M.Science Press. 2002.

Reviewer 2 Report

The present manuscript developed a Phytoplankton index of biotic integrity (P-IBI), Zooplankton index of biotic integrity (Z-IBI), and microbial index of biotic integrity (M-IBI) for the Diannong River in China. The manuscript subject is not novel at global scale, yet the scientific approach and manuscript itself were well concepted, and will have significative impact on Asia region, at least. I only have small suggestions to the authors. Namely:

1)    Please clarify the figure 1. adding a zoom out map, with China country indicate where the study area is in our country. For the majority of readers (non-chinese citizens) will be very important. The legend also needs to have white background to be easily to read.

2)    Please discuss the impact of your study in the application of IBI in our biogeographic region. Your study area (Diannong River) will share similarities with adjacent rivers? What is policy regarding this subject in our country? What is the step forward of your study to this subject?

Author Response

Response to Reviewer 2 Comments

Dear Reviewers:

Thanks for your comments concerning our manuscript entitled “Construction of Aquatic Index of Biotic Integrity and Its Driving Factors in the Diannong River, China” (ID: water-2256894). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and made corrections, which we hope meet with approval. Revised portions are marked in red on the paper. The main corrections in the paper and the responses to the reviewer’s comments are as follows.

Point 1: Please clarify the figure 1. adding a zoom out map, with China country indicate where the study area is in our country. For the majority of readers (non-chinese citizens) will be very important. The legend also needs to have white background to be easily to read.

Response 1: Thanks for your suggestion. We neglected the importance understanding the specific location of study area in the world when when writing the first draft. We have clarified the figure of sampling sites and set white background for the legend of figure. Meanwhile, we have added the map of the location of study area in China (Line 131).

Point 2: Please discuss the impact of your study in the application of IBI in our biogeographic region. Your study area (Diannong River) will share similarities with adjacent rivers? What is policy regarding this subject in our country? What is the step forward of your study to this subject?

Response 2: Thanks for your comment, we are appreciate your suggestion. We have deeply paid attention to the applicability of an article’s findings to the adjacent area and the importance to social trends. So we have added a new section on the possible positive impact of this research on related research in the our biogeographic region and similarities with adjacent rivers. We have explained our policies on this research and the significance of the results of this article for such research (Line 584-624).

We have tried our best to improve the manuscript and made some changes, and we hope that the correction will meet with approval. Meanwhile, we appreciate for reviewer’s warm work earnestly. Once again, thank you very much for your comments and suggestions.

Sincerely yours

Lin Lee

Round 2

Reviewer 1 Report

The authors have tried to improve the manuscript.